Anatomy and Physiology / Unit 7: The Endocrine System
7.4 Pancreas, Blood Glucose and Diabetes
Notes
The pancreas is both exocrine (digestive enzymes) and endocrine. Its hormone-producing cells are in the pancreatic islets (islets of Langerhans).
- Beta cells release insulin when blood glucose is high; insulin lets cells take up glucose, and the liver and muscles store it as glycogen. This lowers blood glucose.
- Alpha cells release glucagon when blood glucose is low; glucagon makes the liver break down glycogen (glycogenolysis) and release glucose. This raises blood glucose.
- This is a negative feedback system with a normal fasting glucose of about 70 to 100 mg/dL.
- Type 1 diabetes: autoimmune destruction of beta cells; no insulin; treated with insulin injections. Type 2 diabetes: cells respond poorly to insulin (insulin resistance), linked to obesity and inactivity; treated with diet, exercise, medication and sometimes insulin.
- Symptoms of high glucose: polyuria (frequent urination), polydipsia (thirst), polyphagia (hunger), fatigue. Long-term damage: blood vessels, nerves, eyes, kidneys.
Practice
After a meal, blood glucose rises. Which hormone is released to bring it back to normal?
Beta cells release insulin, which lowers blood glucose by increasing cell uptake and storage.
A person has not eaten for 12 hours and blood glucose is falling. Which response occurs?
Glucagon stimulates glycogen breakdown in the liver, raising blood glucose.
Which is the main cause of type 1 diabetes?
Type 1 diabetes involves little or no insulin production.
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